Adrian – everything that KWP’s said is generally factual although I doubt that Owners Corporations as your business’ stakeholders would be too impressed with that straight forward approach.
I often say that nothing in Strata is as straight forward as it seems, and as much as I admire your initiative albeit it coming from business-interest, I’m afraid that it’s one of those.
Briefly, the installation of the windows that you provide constitutes an alteration /addition to the common property of the Owners Corporation (O/C), and so requires the prior consent of the O/C via a Motion put to all Owners at a General Meeting, where >75% of those in attendance need to vote in favour in order for the Motion to pass.
If the installation is consented by that means, then the works can proceed subject to any conditions included in the terms of the O/C’s consent, but it’s applicable only to that one project / owner / unit.
The Special By-Law that you refer to only becomes necessary if the O/C, after consenting to the installation, wishes to transfer the responsibility for the on-going maintenance, repair, and replacement of the secondary windows form itself to the current and future Owner/s of the unit concerned.
Special By-Laws of this type need to be agreed to in writing by the Owner who’s to be bound by it, but that’s the only hurdle that I can think of to the O/C voting to create and register a generic Special By-Law permitting the installation of secondary windows (or anything else for that matter), and the O/C could overcome that hurdle by requiring each Unit Owner to so agree at the time that they advise it of a proposed window installation.
So in summary, an O/C may by the process outlined vote to create and register a Special By-Law to permit the installation of your secondary windows, that would apply to all Units in the Plan, and with each Owner then needing (only) to advise the Executive Committee in writing of precisely what is proposed and include a written statement accepting the conditions of that Special By-Law (SBL) and in particular an acceptance of the on-going maintenance responsibilities.
The Office of Fair Trading is right in their advice that “anyone can prepare a by-law” and that it costs “about $100 to submit” ($104.50 actually) to NSW Land Property Information for attachment to the Strata Title of the Plan, but I’d strongly support your desire to consult with an experienced Strata Lawyer such as THIS one who sponsors this forum about possibly preparing “shell” documents (i.e. a SBL and Owner acceptance) that would permit a perhaps parochial O/C to write-in its own conditions (if any) before taking a vote, and if passed to execute and submit it for subsequent registration.